Westwood joined Villa from Crewe Alexandra in 2012 and has become a regular feature under current manager Tim Sherwood.
“I am extremely pleased to sign a new contract and commit my future to Aston Villa,” Westwood told the club’s official website.
“I was made to feel very welcome from the moment I first walked through the door and I’m very happy at the club.
“I believe I’m now entering what I hope will be the peak years of my career and I look forward to spending them here.”
— Ashley Westwood (@ARWesty15) August 12, 2015